The ZU-23-2 was developed in the late 1950s. It was designed to engage low-flying targets at a range of 2.5 km as well as armoured vehicles at a range of two kilometres (km) and for direct defense of troops and strategic locations against air assault usually conducted by helicopters and low-flying airplanes.[2] In 1955, KBP presented the single-barrel ZU-1 and the twin-barrel ZU-14. While the former was eventually dropped, the ZU-14 was selected and, after some modifications, entered series production.[1]

In the Soviet Union, some 140,000 units were produced. The ZU-23 has also been produced under licence by Bulgaria,[3] Poland, Egypt[4] and the People's Republic of China.[5]

Development of this weapon into a self-propelled anti-aircraft gun (SPAAG) led to the ZSU-23-4 Shilka.

The ZU-23-2 (2A13) mounts two 2A14 23 mm autocannons on a small trailer which can be converted into a stationary mount for firing the guns. While in this position the wheels are moved aside. The autocannon can be prepared for firing from the march position in 30 seconds and in emergency can be fired from the traveling position. The weapon is aimed and fired manually, with the help of the ZAP-23 optical-mechanical sight which uses manually entered target data to provide limited automatic aiming. It also has a straight-tube telescope T-3 for use against ground targets such as infantry as well as unarmored or lightly armoured vehicles. The ammo is a feed by a conveyor belt from two ammunition boxes. Each of the ammunition boxes are located on the side of the twin autocannon and each carries 50 rounds. The fumes created by firing the weapon are partially removed through the side openings in the barrels.[2]

Normally, once each barrel has fired 100 rounds it becomes too hot and is therefore replaced with a spare barrel. Each weapon is normally provided with two replacement barrels as part of its standard equipment. Tulamashzavod Joint Stock Company is offering to upgrade the 2A14 guns to the 2A14M standard with a barrel life of 10,000 rounds instead of 8,000 rounds.

The cannon carriage is based on the earlier ZPU-2 anti-aircraft twin heavy machine gun, which mounted two KPV 14.5 mm heavy machine guns. ZU-23-2 can be identified by different placement of the ammunition boxes (at right angles to the gun carriage) and by muzzle flash suppressors. In another similarity to the ZPU series, single-barrel and four-barrel versions of the ZU-23 were also developed. However, these versions never entered service.

ZU-23-2 can be towed by a number of different vehicles. In USSR and later Russia the most frequently used towing vehicles for it were GAZ-664x4 trucks and GAZ-69 4x4 light trucks.[2]

The 23mm AA guns utilizes the same 23x152B case as the wartime VYa aircraft cannon. Due to different loadings and primers the ammunition is not interchangeable, however; ammunition of the anti-aircraft cannon can be identified from its steel casings, ammunition for the aircraft cannon having brass cases instead.[6] The following table lists the main characteristics of some of the available 23x152B ammunition used in 23mm AA guns:

ZU-23-2 entered service with the Soviet Army in 1960. ZU-23-2 is often mounted on trucks for use in both anti-aircraft and fire support roles. It can also be mounted on the roof of the MT-LB multi-purpose tracked APCs. Specially modified three-legged ZU-23-2 is used in BTR-DG based airborne SPAAG. Cheap, easy to operate and still effective, the ZU-23-2 is still used by the Russian Army and by more than 20 other armies.

The type has seen widespread use by both sides in the Libyan Civil War often mounted on technical pickup trucks.[11] The weapon has been heavily used in the Syrian Civil War. YouTube videos depict the weapon bolted on to pickup trucks and one was even successful in shooting down a Syrian helicopter.

ZU-23M - Upgraded variant, designed by the Nudelman Precision Engineering Design Bureau (KB Tochmash). Has new targeting system (which includes laser rangefinder, television channel, optical mechanic device, can be reinforced with thermo location channel and a television system for usage at night) and electromechanic turn system. Optionally, the mount can be fitted with two short-range air-defence missiles, such as the 9M32M "Strela-2M" or the 9M39 "Igla".[12][13]

ZU-23M1 - This is the current model, developed by Open Joint Stock Company Podolsky Electromechanical Plant of Special Engineering “PEMZ Spetsmash” and Closed Joint Stock Company “NTC Elins” and offered by Rosoboronexport. Like the ZU-23M, it has an upgraded fire control system and can optionally be fitted with two launchers for the "Igla" series missile, usually the 9M342 "Igla-S".[14]

The complete air-defence gun/missile system is called ZU-23/ZOM1 (often erroneously called “ZU-23/30M1”). It consists of the "missile-gun firing module" (strel’bovoj modul) ZU-23/ZOM1-SM; the "missile-launching module" (puskovoj modul) ZU-23/ZOM1-PM armed with four 9M333 “Strela-10” missiles; a remote control module (modul distantsionnogo upravleniya) ZU-23/ZOM1-MU and a portable generator AB-1. Depending on the wishes of the client, the system can be delivered without the -SM module (ZU-23/ZOM1-1), without the -PM module (ZU-23/ZOM1-2), without the remote control (ZU-23/ZOM1-3), or without -PM and -MU modules (ZU-23/ZOM1-4).[15]

ZUR-23-2KG "Jodek-G" - Development of ZUR-23-2S with more advanced reflex sight CKE-2 (later CP-1 night-and-day sight with laser rangefinder), electromechanic gun turn system and twin launcher for "Grom" missiles, produced from 2002[16] (pictures).

ZUR-23-2KG-I - Improved export version for Indonesia with CKE-2I sight.

TR-23-2 - Training simulator version of the ZUR-23-2KG-I. The set consists of an instructor's station and a gunner's station (a modified "artillery-missile unit" with the sight replaced by a computer station). Both stations are linked by a wireless network.[17]

ZU-23-2M "Wróbel" - Polish naval version of ZU-23-2, hydraulically powered, produced from 1979.[16]

ZU-23-2MR "Wróbel-II" - Polish naval version of ZUR-23-2S, with Strela-2M missiles and water-cooled barrels, produced from 1986[16][19] (picture).

"Hibneryt" - A ZU-23-2 family gun mounted on specially modified Star 266 truck, truck is fitted with additional ammunition for the gun and modified electrical installation to power guns electromechanic turn system (gun can also work from batteries).

ZU 23-M - Licence version of the ZU-23. It is also known as SH-23M and is produced by Abu Zaabal Engineering Industries (Factory 100).[4]

Nile 23 - Self-propelled version on the tracked M113. A system consists of the combat vehicle with ZU 23-M guns and surface-to-air missiles Saqr Eye, and a tracker vehicle, also based on the M113.[22][23]

Sinai 23 - Similar to the Nile 23, but with the guns and missiles mounted on a TA-23E turret, fitted with a RA-20S E-band radar. Instead of the Saqr Eye, FIM-92 Stinger missiles can be used.[24]

23 ItK 95 - Finnish upgrade of the original 23 ItK 61, designed by Instrumentointi Oy and Vammas Oy. The upgraded gun is equipped with a gyro-stabilized gun, an APU and a laser range finder. ([3]).[12]

SAKO 23 mm/87 - a navalized modernization used by the Finnish Navy. Variants are the 23 M74, the 23 M77, the 23 M80 and the 23 M85. The guns can be removed from M85 carriage and replaced with six Mistral surface-to-air missiles.[25]

Type 80 - Reverse-engineered copy of the ZU-23-2, made by NORINCO.[5] Initially it was offered for export as the G-AA-01.[26] It is referred to as Type 85 gun by some sources.

Giant Bow - Also known as Shengong (Deity Bow, 神弓). This is the name of an air-defense system which consists uf up to eight Type 80 guns and a battery command vehicle (BCV).[5]

Giant Bow II a.k.a. Shengong-II - This is a more modern version of the Giant Bow and is offered for export since 2005. Apart from the 23mm guns, it also comprises TY-90 missile launchers and a 3D radar.[5]

Type 87 - Upgraded version with twin 25mm guns for 25x183B ammunition such as the PG87. After a failed initial design, an improved design was developed in 1979 and ready for evaluation in 1984. The Type 87 gun was accepted for service in 1987. It has the same layout as the original model and consists of two automatic, recoil-operated cannons, a two-wheel cartridge, a Type 86 infrared tracking sight and two 40-round ammunition magazines. The Type 87 fires in either single shot or burst mode, with a cyclic rate of fire of 600~700 rounds/min and has a muzzle velocity of 1,050 m/s.[27]